Higher Cardiorespiratory Fitness Is Associated With Greater Cerebral Blood Flow In Older Adults

PURPOSE: Higher cardiorespiratory fitness (CRF) has been associated with greater gray and white matter volumes and elevated cognitive function in late life. Few studies have examined whether higher CRF is associated with greater cerebral blood flow (CBF). Given regional specificity for associations between CRF and markers of brain health, we predicted that higher CRF would be associated with greater CBF in the hippocampus, anterior cingulate cortex (ACC), and frontal cortical regions. METHODS: We used baseline data from the Investigating Gains in Neurocognition in an Intervention Trial of Exercise study, a multisite 12-month supervised aerobic exercise intervention in older adults aged 65-80. CRF was determined based on a graded exercise test to measure VO2 peak, which, along with participant weight, age, and sex, was used to identify VO2 percentile compared to population normative data. CBF was measured using a pseudo-continuous arterial spin labeling sequence for magnetic resonance imaging. BASIL and Human Connectome Project methods were used for non-linear registration of the CBF data into standard space and to produce voxel-wise comparisons of perfusion. A region-of-interest (ROI) approach was used to focus our predictions on the ACC, frontal lobe, and hippocampus. ROIs were created in native space using FreeSurfer 6.0. In 608 participants with CBF and CRF data, we tested the relationship between CRF and regional CBF using linear regressions in R controlling for site. RESULTS: The sample was mostly female (72%), older (Mage = 70 years), educated (Myears = 16), overweight (MBMI = 29.7 kg/m2), with below-average CRF (MVO2 percentile = 46). 18% identified as Black/African American and 77% White. We found significant positive linear associations between percentile CRF and CBF such that higher CRF predicted greater CBF in all sub-regions of the frontal cortex (B range = .03-.05, p < .05), hippocampus (B range =. 03-.04, p < .05), and ACC (B range = .04-.06, p < .01) when controlling for site. CONCLUSIONS: Findings indicate that higher CRF is associated with greater CBF, a neurobiological marker related to age-related cognitive decline. Therefore, enhancing CRF could be an intervention target to improve CBF in older adults, which could reduce risk of age-related neurocognitive decline. Funded by the NIH (R01AG053952)